Former Prime Minister Yoshiro Mori says Japan should be flexible in resolving the long-standing territorial disagreement with Russia by not sticking too much to the policy of seeking the return of every disputed island off Hokkaido.

Mori, who met with Russian President Vladimir Putin in February in Moscow as a special envoy of Prime Minister Shinzo Abe, is proposing a solution that would use economic cooperation, such as development of the Russian Far East, as leverage.

"It would be great if (both leaders) can agree on instructing their respective foreign ministries to move toward the direction of finding a solution" over the issue, Mori said when asked if progress can be expected anytime soon.

Mori was speaking ahead of a potential visit by Abe to Russia for talks with Putin on April 29. It would be the first official visit to Russia by a Japanese prime minister in 10 years.

The disagreement over who owns the islands of Etorofu, Kunashiri and Shikotan and the islet group named Habomai has prevented the two countries from concluding a peace treaty to officially end World War II.

Mori, who is on friendly terms with Putin, voiced hope that a visit by Abe would be the "start of building new Japan-Russia ties that would have both leaders meeting more frequently."

With Putin having told Mori in February that he wants a "mutually acceptable solution," Mori said Japan now faces the question of whether to change its long-held position that all of the islands must be returned.

"If the stance is 'absolutely four islands' should be returned, the current (stalemate) will just continue," he said.